1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to image-processing technology, and more particularly to reducing the noise of an image sensor.
2. Description of the Related Art
In recent years, with the rapid progress of digital camera technology, digital cameras supporting higher resolutions and various functions have been successively released. There are also many cases where such a digital camera is mounted in other portable appliances such as a cellular phone, a notebook computer, a personal data assistant (PDA) and so forth.
This digital camera is basically provided with an image sensor, such as a Charge Coupled Device (CCD), a Complementary Metal Oxide Semiconductor (CMOS) and the like, for collecting light from a subject and converting the collected light into electrical signals. However, at the present technology level, it is difficult to eradicate noise generation occurring when the image sensor photographs a subject. Therefore, most of the digital cameras have a function for removing or correcting noise, and such a function becomes more and more important in view of the current trend toward high quality images.
Numerous studies have recently been published in relation with noise reduction technology. Related art noise reduction technology includes a circuit-based technique in which high-frequency components are suppressed by passing image signals through a low-pass filter, a technique in which a spatial filter having a planarization function, such as a median filter, is applied to an image, and others. However, most of these techniques have a problem in that some improvement in subjective image quality is accompanied by an impairment of an original image's features, and the number of operations is too large to be suitable for appliances having limited resources, such as digital cameras.